Tunable fiber Bragg gratings for application in tunable fiber lasers

The resonance wavelength of the fiber Bragg gratings (FBGs) is tuned using two methods. Tunable FBGs are used as the selecting elements in the cavities of tunable lasers. An ytterbium-doped fiber laser with a wavelength tuning range of 1063–1108 nm and an output power of 6 W, a Raman fiber laser with a wavelength tuning range of 1252–1303 nm and an output power of 3 W, and an erbium-doped fiber laser with a wavelength tuning range of 1530–1580 nm are realized, and their characteristics are studied.     

Efficient pumping of Rb vapor by high-power volume Bragg diode laser

A 2W cw laser diode (LD) with an external cavity produced by a reflecting volume Bragg grating (VBG) demonstrated a spectral width of 7GHz (full width at half-maximum) at 780nm. The device output power exceeded 90% of the output power of the free-running LD. The emission wavelength was tuned over a 300pm range by thermal control of the VBG. Rb vapor was shown to absorb more than 95% of the laser radiation.     

Tunable dual wavelength emission and bandwidth narrowing of a laser diode array with a simple external cavity

We report on the performance of a commercial, non-AR-coated diode laser bar of 20 W output power, consisting of 20 emitters, which uses an external cavity to achieve tunable, dual-wavelength emission. The separation between the wavelength peaks can be continuously tuned from 0 nm to 5 nm. An output power of 2.9 W is achieved at 3.7 nm peak-to-peak separation and higher powers are achieved for less separation. This is the highest dual wavelength output power reported so far using a standard diode laser array. PACS 42.55.Px; 42.60.-v; 42.60.Da; 42.60.Fc     

Fibre mopfa source of femtosecond pulses with wavelength tunability from 790 to 830 nm

A fibre-optic of sub-150 fs pulse with wavelength tunability from 790 to 830 nm is demonstrated. The output from a gain-switched DFB laser diode at 1552 nm is amplified and compressed in an EDFA generating a soliton-Raman continuum which was then frequency doubled. The output wavelength was tuned over a 40 nm range with very little variation in the pulse duration and output power.     

High-power and wavelength-tunable operation of an Er,Yb fiber laser using a volume Bragg grating

Efficient high-power operation of double-clad Er,Yb-doped fiber lasers with fixed-wavelength and wavelength-tunable resonator configurations using volume Bragg gratings for wavelength selection are reported. The fixed-wavelength laser yielded a maximum output power of 103 W at 1552.6 nm with a linewidth of ~0.4 nm (FWHM) for a launched pump power of 290 W at 976 nm. The wavelength-tunable laser could be tuned from 1528 to 1550 nm with a linewidth of 0.2 nm (FWHM) and with output power in the range 30-38 W for a launched pump power of 120 W. The prospects for further improvement in performance are considered.     

Laser performance of a broadband wavelength tunable Yb:germanophosphate glass with direct diode pumping

The laser performance of a new Yb:germanophosphate(Yb:GP) glass is investigated. A maximum output power of 826 m W at 1063 nm is achieved with direct diode pumping at 976 nm. The wavelength is tuned from 1034.47 to 1070.83 nm, corresponding to a tuning range of 36.36 nm. Thermal lens effects are investigated to optimize the optical cavity.     

High-power and widely tunable Tm-doped fiber laser at 2 μm

Efficient, high-power, and widely tunable Tm-doped fiber lasers cladding-pumped by diode lasers at 791 nm are demonstrated by use of an external cavity containing a diffraction grating. A maximum output power of 62 W is obtained at 2 004 nm for 140 W of launched pump power, corresponding to a slope efficiency of 48% with respect to launched pump power. The operating wavelength is tunable over 200 nm (1 895 to 2 109 nm), with >52 W of output power over a tuning range of 140 nm (1 926 to 2 070 nm). Prospects for further improvement in output power, lasing efficiency, and tuning range are considered.     

10-W-level diode-pumped compact 2.78 microm ZBLAN fiber laser

We report on >9W transverse-fundamental-mode CW output near 3 mum from a 4m heavily erbium-doped ZBLAN double-clad fiber laser pumped by a collimated 100 W 975 nm laser diode array. The pump threshold of the fiber laser was about 1W, and the slope efficiency was 21.3%. The peak wavelength of free running was about 2708 nm at low pump power and moved to around 2785 nm at high pump power. Output of 9W was obtained when the launched pump power was 42.8W. The output, however, fluctuated intensively like a pulsed laser, and the operation broke down with optical damage of the pumping end facet when the pump was increased beyond 42.8 W. Therefore, alleviation of the operation fluctuation, heat management, and strengthening the pumping fiber are crucial considerations for the stable operation of 10-W-level mid-IR ZBLAN fiber lasers.     

Widely tunable,narrow linewidth Tm: YAG ceramic laser with a volume Bragg grating

We report on a widely tunable, narrow linewidth operation of a Tm:YAG ceramic laser. A volume Bragg grating is used in the cavity as a folding mirror for wavelength selection. The wavelength is tuned from 1956.2 to1995 nm, leading to a total tuning range of 38.7 nm. The linewidth is around 0.1 nm over the whole tuning range. A maximum output power of 1.51 W at 1990.5 nm is achieved at 37.8 W absorbed pump power.Different saturation behaviors are observed in the laser performances at different wavelengths.     

High power tunable picosecond green laser pulse generation by frequency doubling of an Yb-doped fiber power amplifier seeded by a gain switch laser diode

A compact tunable high power picosecond green laser pulse source based on frequency doubling of an Yb-doped fiber amplifier seeded by a gain switch laser diode has been developed. The fiber amplifier generates the picosecond infrared pulses with average power of 10.3 W, repetition rate of 1 MHz, pulse duration of 150 ps, and tunable range of 20 nm around 1064 nm. For underwater use, the tunable output infrared pulses are frequency doubled into picosecond green laser pulses, which can be tuned from 527 to 537 nm with average power of more than 1.1 W, corresponding to an overall conversion efficiency of 10.7% by a BBO nonlinear crystal. This kind of laser source will have potential application for underwater optical communication.     

高效率可调谐掺镱双包层光纤激光器研究

研究了一种高效率可调谐掺镱双包层光纤激光器，在抽运半导体激光为915nm、功率为1W的条件下，掺镱双包层光纤激光器的最大输出功率为440mW，输出斜效率约为80％。输出光束的M^2因子为：x方向1．06，y方向1．04。用一光栅作为输出耦合，输出波长可在1070nm-1150nm的范围内调谐。     

基于曲面空间合束的多单管半导体激光光纤耦合

随着单管半导体激光器光纤耦合技术的不断发展,为了进一步提高多单管半导体激光器的输出功率,本文采用曲面空间排列方式对多个单管半导体激光器进行合束研究,使更多数量的单管半导体激光器耦合进入同一光纤中,获得更高的输出功率。文中利用ZEMAX光学设计软件进行仿真模拟,将34只波长为975 nm、输出功率为10 W的单管半导体激光器合束聚焦后耦合进芯径200 μm、数值孔径0.22的光纤中,获得耦合效率91.76%、输出功率312.03 W的激光系统。实验中,将17只单管半导体激光器耦合进芯径200 μm、数值孔径0.22的光纤中,在10.5 A的驱动电流下,输出功率为100.5 W,系统耦合效率为68.46%。     

High power all-solid-state quasi-continuous-wave tunable Ti: sapphire laser system

This paper reports a high power, all-solid-state, quasi-continuous-wave tunable Ti:sapphire laser system pumped by laser diode (LD) pumped frequency-doubled Nd:YAG laser. The maximum tuned output power of 4.2 W (797 nm) and tuned average power of 3.7 W were achieved when fixing the Ti:sapphire broadband output power at 5.0 W and applying 750-850 nm broadband coated mirror.     

All-fiber clad-pumped Tm3+-doped fiber amplifier using high power fiber combiner

The diode laser (LD) clad-pumped 1947.6 nm continuous wave (CW) Tm³⁺-doped fiber amplifier is reported using the master oscillation power amplifier (MOPA) method. The injected seed laser is provided by an all-fiber LD-clad-pumped Tm³⁺-doped single-mode fiber laser, which has a nearly 2.4 W maximal output power and 0.1 nm ultra-narrow linewidth based on the intracore reflection FBG. Using the 25/400 μm double-clad LMA Tm³⁺-doped fiber as the gain fiber, the output maximal output power is 30.6 W from the fiber amplifier, with a slope efficiency of 39.1% respected to the LD total output power. A high power multi-mode fiber combiner is used to couple high power LD light into the gain fiber. The output wavelength is also located at 1947.6 nm, with the slightly expanded laser linewidth of 0.2 nm.     

Diode-pumped 1018-nm ytterbium-doped double-clad fiber laser

We report a 1 018-nm ytterbium-doped double-clad fiber laser pumped by 970-nm diode. A pair of fiber Bragg gratings with reflectivities of 99.9% and 9% at a center wavelength of 1 018.9 nm are employed as cavity mirrors. The ytterbium-doped double-clad fiber is a 2.6-m-long Liekki fiber. Laser output power of 7.5 W at 1 018 nm is obtained under the pump power of 59.2 W. The overall slope efficiency of the fiber laser is about 16%. This low slope efficiency is mainly due to the incomplete absorption of the pump power.     

2080 nm long-wavelength,high-power dissipative soliton resonance in a dumbbell-shaped thulium-doped fiber laser

We demonstrate a 2080 nm long-wavelength mode-locked thulium(Tm)-doped fiber laser operating in the dissipative soliton resonance(DSR) regime. The compact all-fiber dumbbell-shaped laser is simply constructed by a 50/50 fiber loop mirror(FLM), a 10/90 FLM, and a piece of large-gain Tm-doped double-clad fiber pumped by a 793 nm laser diode. The 10/90 FLM is not only used as an output mirror, but also acts as a periodical saturable absorber for initiating DSR mode locking. The stable DSR pulses are generated at the center wavelength as long as 2080.4 nm, and the pulse duration can be tunable from 780 to 3240 ps as the pump power is increased. The maximum average output power is 1.27 W, corresponding to a pulse energy of 290 nJ and a nearly constant peak power of 93 W. This is, to the best of our knowledge, the longest wavelength for DSR operation in a mode-locked fiber laser.     

Internal resonantly enhanced frequency doubling of continuous-wave fiber lasers

In this Letter we describe a simple method for frequency doubling in high-power CW fiber lasers that offers the prospect of very high conversion efficiency and high power in the visible wavelength regime. Our approach is based on second harmonic generation in an enhancement resonator within the fiber laser cavity and does not require active cavity length stabilization. This technique has been applied to a cladding-pumped Yb-doped fiber laser to generate 19 W of linearly polarized CW green output at 540 nm, with excellent temporal stability for 90 W of absorbed diode pump power at 975 nm. The prospects for further improvement in performance with respect to conversion efficiency and output power are considered.     

Diode-end-pumped Tm:GdVO4 laser operating at 1818 and?1915?nm

High power operation at 1818 and 1915 nm has been demonstrated from a Tm:GdVO₄ laser operating in quasi-continuous-wave mode with a maximum measured power of 8.7 W and a laser output energy of 175 mJ was observed in a 20 ms pulse at 1.9 μm. The operation at 1818 nm is the shortest wavelength achieved at multi-watt power levels for a Tm-doped solid-state laser without intra-cavity tuning elements. It has been shown that by careful analysis of the emission spectra, the Tm:GdVO₄ laser can be tuned over a 100 nm wavelength range simply by appropriate selection of the reflectivity of the output coupler.     

1137 nm长波掺镱光纤激光器的出光实验

分别使用976 nm半导体激光器和1040 nm光纤激光器作为泵浦源,实现了1137 nm长波光纤激光器的出光,输出功率均超过百mW。激光器采用相同的线性腔结构,高反光栅和低反光栅的反射率分别为99.6%和39.7%,增益介质是一段8 m长的掺镱光纤,纤芯直径5 m。当976 nm半导体泵浦功率为912 mW时,1137 nm激光输出功率为182 mW,对应的斜率效率为28.5%;当1040 nm激光功率为1.59 W时,输出的1137 nm激光功率为278 mW,斜率效率约为25%。在此基础上对两种泵浦方式进行了对比分析。     

Stable 10 W Er:ZBLAN fiber laser operating at 2.71-2.88 μm

We have developed a diode-pumped tunable 3 μm fiber laser with a cw output power of the order of 10 W with the use of an erbium-doped ZBLAN fiber. A tunability range of 110 nm (2770 to 2880 nm) with an output power between 8 and 11 W was demonstrated. As the pump power was increased, the center of the wavelength range was shifted toward longer wavelengths, but the width of the wavelength range was largely unaffected. The total tunability range for various pump power levels was 170 nm (2710 to 2880 nm). To our knowledge, this is the highest performance (output power and tunability) obtained from a tunable 3 μm fiber laser.